Air Pollution – Key Vocabulary

A comprehensive set of vocabulary flashcards covering composition, pollutants, effects, case studies and control technologies related to air pollution, acid rain and ozone depletion.

Air Pollution

Presence of pollutants in air at levels sufficient to injure living organisms or damage materials.

Troposphere

Lowest atmospheric layer (~0–17 km) where weather occurs and most life exists.

Primary Pollutant

Substance emitted directly into the air from a source (e.g., SO₂ from a smokestack).

Secondary Pollutant

Substance formed in the atmosphere via chemical reactions among primary pollutants (e.g., ozone).

Particulate Matter (PM)

Solid or liquid particles (dust, smoke, soot, aerosols) suspended in air; fine PM < 2.5 µm is most harmful.

Suspended Particulate Matter (SPM)

Concentration of airborne particles measured in µg/m³; CPCB standard for sensitive areas is 100 µg/m³.

Carbon Monoxide (CO)

Colourless, odourless toxic gas that forms carboxyhaemoglobin, reducing blood’s oxygen-carrying capacity.

Carbon Dioxide (CO₂)

Natural atmospheric gas increased by fossil-fuel burning; major driver of global warming though not toxic.

Nitrogen Oxides (NOx)

Group of gases (NO, NO₂) from combustion; contribute to smog, acid rain and respiratory illness.

Sulphur Dioxide (SO₂)

Pungent gas from coal and oil burning; forms sulphuric acid in air, leading to acid rain and bronchitis.

Ozone (O₃)

Tri-oxygen molecule; harmful in troposphere (smog component) but protective in stratosphere against UV.

Photochemical Smog

Air pollution mixture of ozone, PAN and others formed when NOx and hydrocarbons react in sunlight.

Lead Oxide

Particulate lead emitted mainly from leaded petrol; damages nervous system, kidneys and cardiovascular system.

Acid Rain

Wet or dry deposition of acids formed from SO₂ and NOx reacting with water and oxygen in the atmosphere.

Wet Deposition

Acidic rain, snow or fog that delivers sulphuric and nitric acids to ecosystems.

Dry Deposition

Direct fall of acidic gases and particles onto surfaces between precipitation events.

Acid Shock

Sudden influx of highly acidic meltwater in spring that endangers aquatic eggs and fry.

Nitrogen Saturation

Over-fertilization of soils by excess nitric acid, reducing availability of other plant nutrients.

Ozone Layer

Stratospheric region (≈15–30 km) rich in O₃ that filters harmful UV-B radiation.

Ozone Hole

Severe seasonal depletion of stratospheric ozone over Antarctica caused by reactive chlorine and bromine.

Polar Vortex

Strong circumpolar winds isolating cold Antarctic stratospheric air, enabling polar stratospheric cloud formation.

Chlorofluorocarbons (CFCs)

Stable industrial compounds that release chlorine in stratosphere, catalytically destroying ozone.

Catalytic Ozone Destruction

Process where a single halogen atom (Cl, Br) repeatedly converts O₃ to O₂, potentially destroying 100,000 molecules.

Bhopal Gas Tragedy

1984 release of methyl isocyanate in Bhopal, India; over 12,000 deaths and long-term health impacts.

London Smog (1952)

Five-day sulphurous smog episode from coal burning that killed ~4,000 people.

Los Angeles Smog

Photochemical smog dominated by ozone and PAN formed from vehicle exhaust under sunlight.

Meuse Valley Incident

1930 Belgium thermal inversion trapping SOx-laden fog; 63 fatalities from respiratory distress.

Air (Prevention and Control of Pollution) Act, 1981

Indian law setting standards and providing authority to regulate and reduce air pollution.

Central Pollution Control Board (CPCB) Standards

Indian national air quality limits (e.g., SO₂ 30 µg/m³ in sensitive areas).

Electrostatic Precipitator

Device that removes 99 % of particulates by charging them and collecting on oppositely charged plates.

Scrubber

Air-cleaning equipment that sprays water or slurry to remove particulates and SO₂ from exhaust gas.

Cyclone Separator

Spiral flow chamber that uses inertia to drop large particulates from industrial emissions.

Filter Baghouse

Array of fabric bags that physically traps dust from stack gases in power plants.

Catalytic Converter

Vehicle exhaust device using platinum/palladium to convert CO, hydrocarbons and NOx to CO₂, H₂O and N₂.

Lead-Free Petrol

Gasoline without tetraethyl lead; essential for catalytic converters and reduced atmospheric lead.

Green Belt

Buffer zone of vegetation around urban or industrial areas that absorbs pollutants and dust.

Urbanisation

Growth of cities; increases air pollution via dense fuel use, traffic and inadequate planning.

Motorisation

Expansion of vehicle numbers; contributes 50–60 % of urban air pollution in Indian cities.

Industrialisation

Development of industries that emit waste gases and particulates, often without adequate controls.

Indoor Air Pollution

High pollutant levels inside homes, largely from biomass fuel burning, causing millions of deaths annually.